Electrical systems require a power supply. Some electrical systems use more than one power supply in order to provide redundant power in case one of the power supplies fails. Some electrical systems with redundant power supplies have interfaces which allow the power supplies to be inserted into and removed from the electrical system while the electrical system remains in a power-up state. For example, a computer system, such as a computer server, may be required to operate continuously. The ability to swap a new power supply in for one that has failed, while the computer server remains in a power-up state, is crucial.
If the electrical system and the power supply are both in a power-up state during coupling and decoupling of the power supply to the electrical system, there is a possibility of arcing and power surge between the power supply and the electrical system, as is well-known in this field. This can result in flammable debris spilling from the power supply. Additionally, arcing and power surge can damage both the power supply and the electrical system. One way of lowering the possibility of damage due to arcing and power surge is by adding protective circuitry to the power supply and the electrical system.
Another way to reduce the possibility of damage due to arcing is by manually ensuring that the power supply is powered off before coupling the power supply to the electrical system and before decoupling the power supply from the electrical system. However, due to the possibility of human error, this solution lacks a degree of safety. A safe and relatively inexpensive means of ensuring that the power supply is powered down before installing or removing the power supply from an electrical system is desired.